Baby boomers, students, and the elderly all share at least one anxiety: Are my mental abilities holding me back? So it's not surprising that online cognitive exercises, or brain training, are finding a particularly receptive audience these days.

One popular service from Lumosity now has 40 million members. Its exercises are generally entertaining -- if a little humbling at first. New users fill out a very simple questionnaire about their concerns and focus (do you want to better remember people's names or improve your concentration and avoid distractions). Then Lumosity creates a daily regime of exercises for you.

Typical tasks include remembering ever more complex patterns, visual positions, or recalling multiple symbols or images in quick succession. The idea is to continually challenge the user in an attempt to increase particular mental functions, including working memory and executive function. Lumosity is $14.95 a month. A similar program, Posit Science's BrainHQ, is $14 a month. I've tried both and found them each to be engaging -- at least for 20 minutes a day.

With Angelina Jolie' revelations about her breast cancer risk this week, it's particularly interesting to note a new study also released this week of women who had undergone breast cancer treatment. Shelli Kesler, a neuropsychologist at Stanford University, used a subset of Lumosity's exercises to work with 41 breast cancers survivors in order to see if it could help them overcome what can be the mentally enervating effects of cancer treatment. She focused on executive functions, the ability to make decisions.

"This approach has the advantage of adapting and changing the difficulty level," Kesler told FoxNews.com of the computer-based training, which the patients performed on their own, "but were highly motivated." She said most patients exhibited significant improvement in executive functions after the 20- to 30-minute sessions, which occurred four times a week for 12 weeks.

In spite of several studies that show brain training can be effective -- including a large study know as ACTIVE or the Advanced Cognitive Training for Independent and Vital Elderly that showed it can be effective even years after the training is finished -- such cognitive exercises have been controversial. A recent overview of research conducted by professors at the University of Oslo concluded that the exercises only made people better at...doing the exercises. However, the Oslo study only looked at one aspect, working memory, and did not take into account the tremendous variance in the ages of the participants in the studies. In other words, it cast a skeptical eye on cognitive training but was not by any means conclusive.

There is always reason for some skepticism. Even in research that yields positive results, not every person experiences gains. And it can vary depending on the goal. It helped women subjected to chemotherapy but does it help students with learning issues? Can people in their 50's experience improvement or is it too late? (Please don't say it's too late.)

"It's still early days," in cognitive training research Joe Hardy, vice president of research and development at Lumosity told FoxNews.com. Consequently, the company is committed to doing further studies and continually improving its exercises based on new data. He said that's why Lumosity is involved in 38 different university research projects at the moment.

True, other popular, supposedly intelligence enhancing techniques have fallen flat. Crossword puzzles, for example, were supposed to boost our intellectual prowess. However, a recent National Institutes of Health funded study of over 600 individuals demonstrated no appreciable gains from doing the Sunday puzzles, whereas cognitive training exercises did show some positive results.

It's obvious that at a very fundamental level you can train your brain. You can learn a new language or learn how to play the clarinet. But the issue isn't whether practicing an instrument makes you better at playing an instrument. The question is, can brain games make you better at other intellectual endeavors?

In at least one specific area I've found it personally effective: Driving. So-called useful field of view exercises do seem to increase awareness on the road. I found that regular training gave me a heightened focus while behind the wheel, especially in city traffic, and independent studies seem to confirm the effect.

In an era in which healthy kids are taking ADHD drugs just to get better scores on their SATs, online cognitive training looks harmless and possibly quite beneficial. But it's important to note that another factor plays an extremely important role in intelligence and mental alacrity: Exercise. Dr. Kesler emphasizes that exercise is essential in creating new neurons.

Of course, just as all the weight training and cardio workouts in the world won't turn me into Roger Federer, simply exercising your brain on Lumosity won't help you pass a test in American history if you didn't study the revolutionary war. You've got to do some work on your own.

So keep your expectations in check. Remember: Flash cards do make you better at performing mathematical calculations, just don't expect them to turn you into Einstein.